Solar cells are capable of directly converting solar energy to electric energy and increasingly expected as a next-generation energy source, particularly in view of global environmental problems. They come in many varieties including those based on compound semiconductors and organic materials. Silicon crystal-based solar cells are currently popular.
Solar cells can be classified into two categories: those having electrodes both on a light-receiving face through which sunlight enters the solar cell and on a face opposite the light-receiving face (i.e., back face) (“double-side-electrode structure”) and those having electrodes only on the back face (“backside-electrode structure”). The solar cell with a backside-electrode structure has an advantage that the quantity of incoming sunlight increases due to the absence of electrodes on the light-receiving face.
Patent Literature 1, as an example, describes a solar cell with a backside-electrode structure. The solar cell of Patent Literature 1 includes a semiconductor substrate with a back face having i-n junctions and i-p junctions formed thereon, with n-type electrodes on the i-n junctions and p-type electrodes on the i-p junctions. In this solar cell, as sunlight enters the semiconductor substrate through the light-receiving face thereof, carriers are generated in the semiconductor substrate and collected and extracted through the p- and n-type electrodes.